This invention relates generally to ultrasonics and more specifically concerns the measurement of acoustic properties and their changes in liquids, gases and solids.
The two general classes of prior art ultrasonic measuring devices are pulse echo devices and continuous wave (CW) devices. The disadvantages of the pulse echo devices are the acoustic waves are nonmonochromatic and noncoherent, the measurements suffer from broadband and duty cycle effects and the devices usually require very fast rise time electronics and high peak powers leading to instrumentation complexity and expense.
The primary disadvantage of CW devices is "cross-talk" (electrical leakage) which complicates measurement interpretation. This problem requires care to isolate the receiving transducer from the transmitting transducer to minimize the cross-talk. A partial solution to this problem requires a complex transducer having high acoustic coupling yet high electrical isolation. Such a complex transducer is expensive and fragile.
A sampled continuous wave (SCW) device disclosed in a paper entitled A "Sampled-Continuous Wave" Ultrasonic Technique and Spectrometer by J. G. Miller and D. I. Bolef published in The Review of Scientific Instruments, Vol. 40, No. 7, pages 915-920, July 1969, gates off the CW source and waits for the acoustic decay sampling as desired. This comes close to a CW ultrasonic measuring device with no cross-talk; however, it has the disadvantage that it is duty cycle bound. That is, the ratio of signal time to time for a complete cycle is low.
It is, therefore, a primary object of this invention to provide an ultrasonic measuring instrument that has no cross-talk.
Another object of this invention is to provide an ultrasonic measuring device that has nearly one-hundred percent duty cycle.
A further object of this invention is to provide an ultrasonic measuring device that requires only a very simple transducer.
Still another object of this invention is to provide a simple, inexpensive, portable, yet accurate means for measuring acoustic properties and their changes in liquid, gases, plasmas and solids.
Other objects and advantages of this invention will become apparent hereinafter in the specification and drawings.